Understanding pre-operative and post-op factors that influence post-surgical pain management success may provide clues in preventing progression to chronic pain after surgery, according to research presented at the American Pain Society (APS) Annual Scientific Conference.
“Post-operative pain, its consequences and response to treatment, vary greatly among patients,” said Timothy Brennan, MD, University of Iowa Medical Center, Iowa City, Iowa. “Most postoperative pain resolves; however, chronic pain after surgery and continued medication use are increasingly recognised as important perioperative problems.”
He added that post-operative pain is a model of not only acute pain, but the development of chronic pain. In general, research shows that reducing pain with various analgesic treatments has been successful for pain management in the acute postoperative period, but there are exceptions.
“Although we assume that good treatment of acute post-surgical pain will prevent chronic pain, higher severity of acute pain during the first 3 days after surgery is associated with greater likelihood for progression to chronic pain,” said Dr. Brennan.
He explained that since most surgeries are elective, there usually is time to assess patients prior to surgery to predict the impact of pre-and post-op variables that could influence whose pain resolves and whose doesn’t.
“We know that procedure-specific chronic conditions occur after common operations, such as the severe pain associated with breast and cardiac surgeries and orthopaedic joint replacements,” said Dr. Brennan. “However, it has been very difficult to understand the pathogenesis, prevention and treatment of postoperative chronic pain. Also, it is well known that psychosocial factors strongly impact transition from acute to chronic pain. Limited coping ability, depression, and anxiety can predict poorer acute pain control and advancement to persistent postsurgical pain.”
He noted that opioids remain the primary therapeutic strategy for treatment of acute post-op pain, but opioid requirements and pain can vary greatly among patients — even for the same surgery. Minimally invasive procedures typically cause less pain than open surgeries, and a variety of opioid-sparing strategies can be employed, such as peripheral nerve blocks, inter-operative ketamine administration, neuraxial infusion of local anaesthetics, and oral or intravenous NSAIDS, COX-2 inhibitors and acetaminophen.
Sometimes treatment success may require high doses of opioids, and Dr. Brennan noted that those involved in perioperative care need better understanding about long-term use of opioids after acute post-op pain.
“We need to learn more about long-term use of opioids after acute postoperative pain and identify patient subgroups at high risk in order to reduce progression to chronic opioid use,” he said.
Dr. Brennan added that further studies are needed to help predict which surgical patients are most likely to develop chronic pain and continue using opioids and other drugs.
“In future studies, batteries of psychosocial variables could be assessed before and after surgery in larger numbers of patients,” he said. “Measures of neuropathic pain, mood and function can be added to assess the impact of these factors on pain outcomes.”